[OOBE] Out of box experience window (#9973)

src/settings-ui/PowerToys.Settings/App.xaml

@@ -1,7 +1,7 @@
 <Application x:Class="PowerToys.Settings.App"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             StartupUri="MainWindow.xaml">
+             Startup="Application_Startup">
     <Application.Resources>
          
     </Application.Resources>